Bullinger was born in 1504, the son of a priest. When his parents converted to Protestantism later in life, they were married. While he was a student in Cologne, he decided to leave the Catholic church after reading the works of Luther and Melanchthon and soon after became an ally of Zwingli, the famous Swiss reformer. He actually replaced Zwingli as the new pastor in Zurich following Zwingli’s death. Much of his theology was built on the idea of the covenant, which he shared with Zwingli and continued in the pulpit where he preached almost daily in Zurich. His collection of sermons entitled Decades was published, and he also wrote a history of Switzerland including three volumes on the Reformation. He was sought after for pastoral counsel throughout Europe, and worked with Calvin on uniting their Protestant groups on issues like The Lord’s Supper. He died in 1575, having strengthened and grown the Reformation in Switzerland that Zwingli helped to start.